Temporal Tree of Thought: Reasoning-Guided Visual Cue Search for Long-Video Understanding

Ziling Huang, Shin’ichi Satoh


Abstract
Long-video understanding remains challenging for Multimodal Large Language Models (MLLMs) due to limited context length. Uniform sampling may miss crucial moments, while agent-based frame video understanding methods often evaluate frames independently, overlooking the temporal organization of videos. Ideally, evidence selection should mimic how humans answer questions about long videos: first locating the relevant segment from the global context, then zooming into local objects, and details. We propose Temporal Tree of Thought (T3), a training-free framework for adaptive coarse-to-fine long-video understanding. T3 constructs a question-agnostic hierarchical temporal tree via recursive temporally constrained clustering, where each node represents a contiguous segment with an informative key frame. During inference, T3 performs an answer–retrieve–explore loop: it reasons over coarse representative frames, generates a search statement when evidence is insufficient, and expands relevant branches for finer-grained evidence. This process adaptively shifts the search target from temporal regions to specific objects, and visual details to help video understanding. Experiments on VideoMME, LongVideoBench, and LVBench show that T3 improves Qwen2.5-VL-7B by 0.5%, 4.6%, and 4.4%, respectively, under the same frame budget, demonstrating the effectiveness of structured temporal reasoning. We will release code.
Anthology ID:
2026.findings-emnlp.630
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
13233–13251
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.630/
DOI:
10.18653/2026.findings-emnlp.630
Bibkey:
Cite (ACL):
Ziling Huang and Shin’ichi Satoh. 2026. Temporal Tree of Thought: Reasoning-Guided Visual Cue Search for Long-Video Understanding. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 13233–13251, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Temporal Tree of Thought: Reasoning-Guided Visual Cue Search for Long-Video Understanding (Huang & Satoh, Findings 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.findings-emnlp.630.pdf